Method of making inner tubes



Way 7, 1929. B. c. EQERHARD 1,712,335

METHOD OF MAKING INNER TUBES Filed March 10, 1928 Zlmwxntor Boyd C. Eberhard composed of a as cred into suitable lengths Patented May 7, 1929.

1,712,335 PATENT OFFICE.

BOYD O. EBERHARD, OI AKRON, OHIO, ABSIGNOR TO THE GOODYEAR TIRE & RUBBER COMPAN Y, OF AKRON, OHIO, A CORI 'ORA'I'ION OF OHIO.

METHOD OI LIA KING INNER TUBES.

Application filed larch 10, 1928. Serial No. 280,812.

My invention relates generally to a method ofmolding annular articles, and it has particular relation to a method of the above designatedcharacter for manufactur- 8 ing reinforced molded inner tubes for pneu- -matic tire casin One object of the invention is to rovide a method of manufacturingmolde inner tubes in which the outer and inner periph- 1e eral portions thereof will have substantially equal thicknesses.

Another object of the invention is to provide a method of 'manufacturing mo ded inner tubes, having relatively uniform thicklt nesses at the outer and inner peripheral portions thereof, by employing continuous strips of stock having substantially uniform thicknesses.

Prior to the invention, molded inner tubes for pneumatic tire casings have been manufactured by a method involving the employment of an extruding machine having a slightly eccentric die which formed a continuous tube having a non-uniform thick- 25 ncss. The continuous tube was severed into predetermined lengths which were so spliced at their opposite ends as to form an annular tube having an outer peripheral portion which was substantially thicker than the inner peripheral portion thereof. The tube was inserted in a mold and inflated by the application of compressed fluid to the interior thereof, which caused the relatively thick outer peripheral portion to be'slightly. as stretched in conforming to the confi ration of the mold cavity. Consequently, t e thickness of the outer peripheral portion of the tube was decrease slightly to a value sub stantially equal to the thickness of the inner no peripheral portion thereof. The outer and inner peri heral portions of the tube, when removed road the mold retained the relative' thickness established therein.' p

e invention comprises a method of as manufacturing molded inner tubes of uniform thickness b the employment of a continuously forme laminated strip which is plurality of. separately formed strips having substantial] uniform as thicknesses. One of the separate y formed strips is relatively narrower than the others and this strip is super osed upon the others at one side of the mi dle portions thereof. Thus reinforced, th laminated strip is sevof material which are spliced at opposite ends and folded to form annular tubes. In each of the tubes the reinforced portion is located at the outer periphery thereof. The tubes are separately inflated and cured in an annular mold, wherein. the thickness of the reinforced portion of a tube is reduced until it is equal substantially to the thickness of the inner peripheral portion thereof.

For a better understanding of the invention, reference may now be had to the accompanying drawings, forming a. part of this specification, in which: I

Fig. 1 is a diagrammatical illustration of an ap aratus for manufacturing inner tubes accor ing to one form of theinvention;

Fig. 2 is a fragmentary cross-sectional view of a tube-forming drum taken substantially on line IIII of Fig. 1;

Fig. 3 also is a fragmentary cross-sectional view of a tube-forming drum taken substantially on line II-II of Fig. 1 and illustrating a method of forming a tube upon the drum; and Fig. 4 is a fragmentary cross-sectional view of a mold employed in curing inner tubes for pneumatic tire casings.

In practicing the invention, rubber-stri s tially aplurality of equa widths, are formed b a contin uous y operating calenderlO. conveyor- 14 transports the stri 13 to a o'sition adjacent one of the calbnder re s emplo ed in forming the strip 11 where it is stitc ed to the latter by a roll 16. A twoply stri 17, comprising the united strips 11 and L is transported by a conveyor 18 and deposited on a conveyor 19, where it is united with the strip 12 to form a three ply strip 20. As best shown b Fig. 2.the strips 11, 12 and 13 composing t e strip are so assembled as to provide progressively ste ped margins between the adjacent edges 0 the strips.

A small calender 21, positioned above the conveyor 19, forms a ativel narrow conm tinuous strip 22, which is stitc ed by'a' roller 23 along one side'of the strip 20 to form a strip 24 composed of longitudinal portions having three and four ply thicknesses. The strip 24 is suspended m a loop 26 between the conveyor 19- and an intermittently .0 erating roller 27 which discharges the strip 24 upon an intermittently operating conveyor 28. 4 The conveyor 27 are operable simultaneously and at subm 11, 12 and 13, having substam,

28 and the roller length of the strip 24 deposited u stantially equal peripheral speeds. The

conveyor 28 is severed by the operation of a cutter 29 acting against a bar 31 which is dis sed transversely with respect to the strip 24 between theendof the'conveyor 28 and the roller 27. A blank 32, formed by the operation of the cutter 29, then is removed from the conveyor 28 and is formed into an endless band upon a drum 33. An edge of the blank 32, having the strip 22 deposited thereon, is then folded over the remaining portion of the strip and stitched to the op osite edge thereof.

It will e noted that the inner peripheral portion of a tube 34 thus formed is composed of three-ply material while the outer ortion thereof has a four-ply thickness. ereafter the tube 34 is removed from the drum 33 and inserted in a suitable mold 36 where it is inflated and cured by steam within the jackets 37 thereof. \Vhen the outer peripheral portion of the tube 34 is expanded, in order to occupy the outer peripheral portion of themold 36, its thickness becomes substantially equal to the thickness of the inner perip eral portion thereof.

From the foregoing description, it is apparent that the invention embodies a very eflicient and economical method of making inner tubes for neumatic tire casings. Ob viously the resu ting product has many featurcs and advantages that are not embodied in inner tubes which have been constructed by other methods heretofore employed.

Although I have illustrated but the preferred form which the invention may as sume, and have described that form in detail, it will be apparent to those skilled in the art that the invention is not so limited, but that various modifications may be made therein without departin from the spirit of the invention or from t e scope of the appended claims.

pon the r What I claim is:

1. A method of making rubber tubes which comprises continuously forming a strip of rubber tube stock, continuously formin and applying to the first strip, a relativey narrow reinforcing strip, severing the assembled strip into blanks, forming the blanks into endless tubes and then molding the tubes.

2. A method of making rubber tubes which comprises continuously forming a strip having reinforced portions longitudinally thereof, formin the strip into endless tubes, and then molding the tubes.

3. A method of making rubber tubes which comprises continuously forming a relatively wide, and a narrower rubber strip, progressively stitching the strips together, forming the com osite strip mto endless tubes and then mo ding the tubes.

4. A method of making rubber tubes which com rises'continuously forming a relativel wi e, and a narrower rubber strip, stitching the strips together, forming the composite strip into endless tubes and molding the latter with the narrower strip around the outer peripher thereof.

5. A method 0 molding rubber which comprises continuously forming a relatively wide, and a narrower rubber strip, progressively stitching the strips to ether, severing the com site strip into blanks, forming the bla into endless bands, folding the portion of the band, having the narrower strip thereon, over upon the remaining portion thereof, stitching the edges of the band together to form a tube, and curing the latter in an annular mold.

In witness whereof, I have hereunto signed my name.

Signed at Akron, in the county of Summit and State of Ohio, U. S. A., this 9th day of March, 1928.

, BOYD C. EBERHARD. 

